1. Field of the Invention
The present invention relates to a hydrodynamic bearing assembly and a spindle motor having the same.
2. Description of the Related Art
In general, a small spindle motor used in a recording disk driving device (e.g., a hard disk drive (HDD)) includes a hydrodynamic bearing assembly. A lubricating fluid such as oil is filled in a bearing clearance of the hydrodynamic bearing assembly. The oil filled in the bearing clearance is pumped by a dynamic pressure groove to form hydrodynamic pressure to rotatably support a shaft.
During rotation and driving of a rotor, bubbles can be formed in the lubricating fluid filled in the bearing clearance. A circulation hole may be formed in a sleeve in order to discharge the bubbles from the lubricating fluid.
That is, the bubbles may be discharged from lubricating fluid filled in the bearing clearance outwardly through the circulation hole.
However, lubricating fluid may not circulate, and that is, may not move due to process tolerance or assembly tolerance of a sleeve or shaft.
Thus, bubbles may not be discharged outwardly from a bearing clearance.